The present invention relates to carbon aerogels, electrochemical cells and systems for deionization and purification of water effluents.
Resorcinol is a well-known material commonly used in resins, dyes, adhesives, pharmaceuticals, and other applications. It can be obtained in a variety of grades and forms, such as crystals, flakes, pellets, and the like. Resorcinol, in its various forms, is soluble in water, alcohol, ether, benzene, glycerol and formaldehyde.
As disclosed in U.S. Pat. No. 5,425,858 to Farmer, resorcinol can be used to synthesize carbon aerogels. Specifically, carbon aerogel can be produced by the polycondensation of resorcinol and formaldehyde in a slightly basic medium, followed by supercritical drying and pyrolysis in an inert atmosphere. Thin electrodes formed from such carbon aerogels may be used in capacitive deionization applications, as disclosed in this reference, whose contents are incorporated by reference in their entirety.
The thin electrode plates (approximately 0.25 mm thickness) formed by this process, however, have a number of drawbacks. First, they are prohibitively expensive to use on a commercial scale, costing on the order of $1000/square inch of surface area. Second, a device using these electrodes has only been effectively driven at voltages and currents lower than those at which water is electrolyzed. Also, the thin nature of the plates limits the deionization capacity. The thin plates are not self supporting and it is difficult to make a direct reliable electrical connection with these. Finally, these electrodes are glued to a titanium plate and so one of each of these plates is unavailable for use as a deionization surface.